Off-set tow target



March 1957 w. c. WOODWARD ETAL 3,

OFF-SET TOW TARGET Filed Jan. 29, 1965 INVENTQRS WILMER C. WOODWARD HEODORE C. HERRING ATTORNEYS United States Patent Office 3311,3 Fatented Mar. 28, 1967 3,311,376 OFF-SET TOW TARGET Wilmer C. Woodward, Blue Bell, and Theodore C. Herring, New Hope, Pa., assignors to the United States of America as represented by the Secretary of the Navy Filed Jan. 29, 1965, Ser. No. 429,176 12 Claims. (Cl. 273105.3)

The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

The present invention relates to aerial tow targets and more particularly relates to an aerial tow target capable of flying a flight path that is offset laterally from that of the towing vehicle.

To evaluate and determine airborne and surface missile weapon system effectiveness against multiple targets, a need has arisen for a towed target which is capable of following a flight path parallel to, but separated in lateral distance from a towing vehicle. This vehicle may be itself a powered target or a manned aircraft. It is of particular necessity that the targets used be capable of multiple-target presentation and that the presentation used for the missile firing exercises have a fixed pattern which may be reliably attained each time the targets are flown at a given altitude, speed and tow line length.

In the past, attempts have been made to satisfy the requirements of multiple target presentation and reliable formation control by the use of powered targets. This approach has been unsuccessful and extremely costly. Also, attempts have been made to satisfy the aforementioned requirements by providing incidence in the vertical tail fin of the standard towed target. This method resulted in insufficient flight path separation, measured normal to that of the towed vehicle, and stability only over a very limited range of speed.

The present unique off-set tow target meets the aforedescribed requirements by using vertical canards in conjunction with vertical flns, both surfaces having the required degree of incidence to develop a large side force on the target (normal to the vertical fin and canard) while at the same time providing the proper degree of stability to trim the tow target into the airstream at a slight nose-out attitude and provide necessary stability in the yaw-plane. Slight nose-out body trim provides additional body side-force to add to the vertical fin and canard side force. Longitudinal stability of the target is provided by the horizontal fins which have zero incidence. In addition, the offset towed target of the present invention is towed from the center of gravity, or other selected point on the longitudinal center line axis of the body, as opposed to being towed from a tow point on the outer skin of the target. Because of this first technique, the line of force of the tow line alw-ays passes through the center of gravity, which is not the case with the tow point on the outer surface of the target. With the tow point thus fixed at one point for all flight conditions of speed, altitude and Mach number, the aerodynamic center of pressure of the target is selected so that the tow target remains stable at all speeds up to the design limits selected. Additionally, a narrow longitudinal slot is provided on the skin of the tow target, through which the tow line egresses from the tow target. The angular position of this slot is selected such that any roll-attitude deviation from the desired roll attitude of the target (normally vertical fins and canards in vertical plane) will cause the side edge of the narrow slot to bear on the towline, thus developing a rolling moment in the correct direction to trim the tow target in roll at all times.

An object of the present invention is the provision of a tow target capable of following a flight path parallel to, but separated in lateral distance from, a towing vehicle.

Another object is to provide an offset tow target for missile system evaluation, which target is capable of flying a fixed-pattern multiple target presentation.

A further object of the invention is the provision of an offset tow target capable of providing the same presentation pattern each time the target is flown at the same conditions of altitude, speed and cable length.

Still another object is to provide a reliable, inexpensive, simple tow target adapted to fly a flight path which is offset laterally from the towing vehicle and which when simultaneously used with other similar type targets provides a multiple tar-get presentation for evaluation of missile systems, the presentation being uniform for each use thereof at identical conditions of altitude, speed and cable length.

Various other objects and advantages will appear from the following description of an embodiment of the invention, and the novel features will be particularly pointed out hereinafter in connection with the appended claims.

In the drawing:

FIG. 1 shows a top plan view of a multiple target presentation utilizing the offset target of the present invention.

FIG. 2 illustrates a side elevation, partly in section, of one of the targets of FIG. 1.

FIG. 3 illustrates a plan view of the target of FIG. 2.

FIG. 4 is a cross-sectional view taken along the line 44 of FIG. 2; and

FIG. 5 is a schematic representation of the interaction of the tow cable and the slot formed in the skin of the target.

In the illustrated embodiment of the invention there is shown in FIG. 1 a towing aircraft generally noted at 10 having connected thereto, through cable 15, a pair of targets 20a and 20b which follow a flight path parallel to but separated in lateral distance from the towing aircraft 10.

It is understood that the towing vehicle 10 may itself be a powered target or a manned aircraft and that targets 20a and20b may be connected to other than the tail section as illustrated in FIG. 1. For example, each target or both targets may be connected to the wing while another target having no offset capability may be connected to the tail section. It is therefore obvious that many permutations and combinations of the basic concepts embodied herein may be utilized to provide multiple target presentations other than the equilateral triangular presentation of FIG. 1.

Referring now to FIG. 2 for a detailed description of the target 2611 of FIG. 1, there is shown a target specifically constructed to fly along a path offset to the left of the towing vehicle 10. It should be understood that the construction of target 20b is opposite to that of target 20a thereby providing a target which follows a flight path offset to the right of the flight path of the towing vehicle.

Target 20a includes a relatively thin-skin, tubular body 21 of cylindrical configuration which may be constructed of plastic, cardboard, or like inexpensive and light weight material. The forward end 21a of the target 20a is constructed with a nose assembly 22 which for purposes of the present invention is a radar augmentation device such as the commercially well known Luneberg lens. The purpose of radar augmentation and this lens in particular is to increase the radar return from targets which, of themselves, provide insufficient return to satisfy the need of the various weapon systems. This deficiency may be due to the small physical size of some targets or to a need for unrealistically large return during the developmental testing of a missile system. It is obvious that alternatively, the nose assembly 22 may contain, in lieu of the radar augmentation lens discussed above, a missile scoring system such as that described and disclosed in U.S. Patent No. 3,091,463 to M. J. Cohen et al., issued May 28, 1963. It is further obvious that other special instrumentation may be included in the aerial target to make the same suitable to accomplish the test objectives of the various missile systems. It should be further noted that although one Luneberg lens is shown that others may be placed at the aft section of the cylindrical body 21 and at an intermediate portion -for purposes of providing radar augmentation to the right and left of the target.

Vertical canards 3t) are positioned and appropriately connected to the forward end 21a of the cylindrical assembly 21. These vertical canards can either be formed as a pair of vertical elements extending from the body or skin of the target or may alternatively be formed of a unitary element which extends through the body of the target.

A pair of vertical fins 40 and a pair of horizontal fins 50 are positioned at the aft or rear section of the target 20a and also are appropriately fastened by means well known and used in the art to the aft section. As above, the vertical fins 40 and horizontal fin 50 may be constructed of individual elements secured to the body section or as a unit 'for application thereto through slots formed in the body portion.

As viewed more clearly in FIG. 3, both the vertical canards 30 and the vertical fins 40 are set at prescribed angles of incidence oz and B, respectively. These angles, which are shown exaggerated for purposes of illustration, are set relative to the vertical plane VV of the target to trim the target 20a at zero to a slightly nose-out flight attitude and to produce the desired side forces on the target to cause the same to fly a flight path that is offset laterally, in this case, to the left, from that of the towing vehicle 10. A small additional side force is acnieved with the target body at a slight nose-out attitude. Incidence angles a and 5 are determined from the degree of separation required, the tow line length, the altitude at. which the target will be towed and the speed at which the target will be towed. For purposes of illustration and not limitation, an angle a of 6 degrees and an angle {3 of 2 degrees will provide a 60 lb. target with 200 ft. of lateral separation from the towing aircraft when the target is streamed to a length of approximately 550 ft. at an altitude of 20,000 ft. and speed of Mach 0.6.

The tow line connection assembly generally noted at 60 for connecting the tow target 20a to the towing aircraft 10 will now be described with specific reference to FIGS. 2 and 4. A pair of longitudinally spaced bulkheads 61a and 61b are positioned intermediate the length of the target body 21 and straddle the center of gravity (06.) of the composite target 20a. The bulkheads 61a and 61b support a tube 62 which extends parallel to but is oifset from the longitudinal axis or roll axis of the target body 21. A clevis member 63 is fastened to the tube assembly 62 at the center of gravity of target 20a and pivotally secures a hinge member 65 thereto through pivot pin 63a. The tow cable passes through a slot 70 formed in the skin 21 of the target a and the end of the cable 15 is connected to the hinge member 65.

As viewed more clearly in FIG. 4, the longitudinal slot 70, including sidewall 70a, has an acute angular position relative to the horizontal axis HH. The tube 62 is radially offset from the longitudinal center line or roll axis of the body 21 a distance to insure that the pivot pin 63a of the clevis member '63 crosses the longitudinal center line of the body 21 at the CG. The clevis 63 face toward the longitudinal slot 70 and the pivot pin 63a extends normal to a plane passing through the slot 70 and the longitudinal center line. Therefore, the hinge 65 also pivots in the plane extending between the slot and the center line and the cable 15 secured to the hinge 65 will egress from and pivot along the longitudinal slot 70 with- 4. out engaging sidewall a, if the target is in the desired roll attitude.

Referring now to FIG. 5, the desired roll attitude of the towed target during offset towing, which i normally with vertical fins and vertical canards in the vertical plane, is controlled by the angular position of the longitudinal slots 70 along the target skin 21. Since the tow line is attached to the target at the CG. position on the roll axis of the tow target, any .roll attitude deviation 5 from the desired attitude as controlled by the angular location of the slot, produces a corrective rolling moment on the target by reason of the side edge 70a of the narrow slot 70 hearing on the tow line 15. The resulting counter force denoted at F tends to rotate the body about the roll axis through the angular deviation 6.

For purposes of illustration and not limitation, when the target is used for offset flight path towing in high-speed, high-altitude regions, the slot is positioned 20 degrees above the horizontal reference plane H-I-I of the target 20a. For high-speed, low-altitude flight conditions, the slot may be positioned 10 degree above the horizontal. These angular positions are selected to maintain the roll attitude of the tow target substantially within plus or minus 5 degrees of the normal horizontal fins-level flight attitude.

It is contemplated by the present invention that alternative features may be utilized. For example, in lieu of the single longitudinal slot shown, a plurality of slots may be formed at varying angular relations with respect to the horizontal reference plane H-H to enable the target to be utilized at varying conditions of speed and altitude. Additionally, it is contemplated by the present invention that the vertical cauards and vertical fins may be adjustable to provide varying angles of incidence and, moreover, that the same may be remotely controlled by the towing aircraft during flight conditions.

It should further be understood that more than the two targets 20a and 20b may be towed by the towing vehicle and that the lateral deviation or offsets from the towing vehicle may be varied to obtain differing formations by changing the angles of incidence CL and ,9, the length of cable 15 and the weight of the cable 15.

It will be understood that various changes in the details, materials, steps and arrangement of parts, which have been herein described and illustrated in order to explain the nature of the invention, may be made by those skilled in the art and within the principle and scope of the invention as expressed in the appended claims.

What is claimed is:

1. An aerial tow target for flying a flight path that is offset laterally from that of a towing aircraft to which the target may be attached by a towing cable or the like, comprising:

an elongated body member;

vertical canard means secured to one end of said elongated body member;

vertical and horizontal fin means secured to the other end of said elongated body member; said vertical canard means and said vertical fin means having an angle of incidence relative to the longitudinal axis of said body member, whereby, when said body member is towed by an aircraft, said body member flys a flight path which is offset laterally from that of the towing aircraft; fastening means attached to said body portion for connecting the towing cable to the target; and

means on said body member for cooperating with the towing cable to maintain the target at a desired roll attitude.

2. The target as defined in claim 1 wherein said body member is of hollow, cylindrical configuration.

3. The target as defined in claim 1 wherein said fastening means is located at the center of gravity of the target.

4. The target as defined in claim 1 wherein the fastening means is located at the center of gravity of the target and also at the longitudinal center line thereof.

5. The target as defined in claim 4 wherein said means cooperating with the towing cable includes a longitudinal slot formed in said body member for permitting egress of the towing cable from the interior of the target, said slot being located at an acute angle relative to the horizontal plane of the target.

6. The target as defined in claim 5 wherein said fastening means is in alignment with said slot thereby permitting egress of said cable without the same engaging the sidewalls of said slot when the target is in the desired roll attitude and whereby any roll attitude deviation from the desired roll attitude of the target will cause the side edge of the slot to bear on the towing cable, thus developing a rolling moment in the correct direction to trim the tow target in roll.

7. The target as defined in claim 6 wherein ing means includes:

a fixed member positioned at the center of gravity of the target and also along the roll axis thereof; and hinge means connected to said fixed member and pivotable about an axis normal to a plane passing through the slot and the roll axis of said target.

8. An aerial tow target for flying a flight path that is offset laterally from that of a towing aircraft to which the target may be attached by a towing cable or the like, comprising:

an elongated hollow body member of cylindrical configuration;

vertical canards secured to one end of said body member;

vertical and horizontal fins secured to the other end of said body member;

said fastensaid vertical canards and said vertical fins having an acute angle of incidence relative to the vertical plane of the target;

a longitudinally extending slot formed in said body member for permitting egress of the towing cable from the interior of the target, said slot located at an acute angle relative to the horizontal plane of the target;

a support means secured within said body member, said support means extending parallel to said body member and offset from the roll axis thereof;

a clevis assembly including a pivot pin secured to said support means at the center of gravity of said target, said pivot pin located at said roll axis and normal to a plane passing through said longitudinal slot and said roll axis;

and hinge means pivotally secured by said pivot pin to said clevis assembly and pivotal in said plane passing through said longitudinally extending slot and said roll axis, said hinge means formed for connecting the towing cable thereto; whereby said hinge means is in alignment with said slot thereby permitting egress of said cable without the same engaging the sidewalls of said slot when the target is in the desired roll attitude and whereby any roll attitude deviation from the desired roll attitude of the target will cause the side edge of the slot to bear on the towing cable, thus developing a rolling moment in the correct direction to trim the tow target in roll. 9. An aerial tow target for flying a flight path that is offset laterally from that of a towing aircraft to which the target may be attached by a towing cable or the like, comprising:

an elongated body member; means secured to one end of said elongated body member for developing side forces on the target;

means secured to the other end of said elongated body member for stabilizing and developing side forces on the target, whereby said two recited means cause said body member, when towed by an aircraft, to fly in a flight path which is offset laterally from that of the towing aircraft; fastening means attached to said body member for connecting the towing cable to the target; and

means on said body member for cooperating with the towing cable to maintain the target at a desired roll attitude.

10. The target as defined in claim 9 wherein the fastening means is located at the center of gravity of the target and also at the longitudinal center line thereof.

11. The target as defined in claim 10 wherein said means cooperating with the towing cable includes a longitudinal slot formed in said body member for permitting egress of the towing cable from the interior of the target, said slot being located at an acute angle relative to the horizontal plane of the target.

12. The target as defined in claim 11 wherein said fastening means is in alignment with said slot thereby permitting egress of said cable without the same engaging the sidewalls of said slot when the target is in the desired roll attitude and whereby any roll attitude deviation from the desired roll attitude of the target will cause the side edge of the slot to bear on the towing cable, thus developing a rolling moment in the correct direction to trim the tow target in roll.

References Cited by the Examiner UNITED STATES PATENTS 2,400,400 5/1946 Duer 244-3 2,779,553 1/ 1957 Troxell. 2,821,396 1/1958 Seeley 273105.3 2,918,285 12/1959 Franklin 273l05.3 3,223,418 12/1965 Norman et al. 273-1053 RICHARD C. PINKHAM, Primary Examiner. M. R. PAGE, Assistant Examiner. 

9. AN AERIAL TOW TARGET FOR FLYING A FLIGHT PATH THAT IS OFFSET LATERALLY FROM THAT OF A TOWING AIRCRAFT TO WHICH THE TARGET MAY BE ATTACHED BY A TOWING CABLE OR THE LIKE, COMPRISING: AN ELONGATED BODY MEMBER; MEANS SECURED TO ONE END OF SAID ELONGATED BODY MEMBER FOR DEVELOPING SIDE FORCES ON THE TARGET; MEANS SECURED TO THE OTHER END OF SAID ELONGATED BODY MEMBER FOR STABILIZING AND DEVELOPING SIDE FORCES ON THE TARGET, WHEREBY SAID TWO RECITED MEANS CAUSE SAID BODY MEMBER, WHEN TOWED BY AN AIRCRAFT, TO FLY IN A FLIGHT PATH WHICH IS OFFSET LATERALLY FROM THAT OF THE TOWING AIRCRAFT; FASTENING MEANS ATTACHED TO SAID BODY MEMBER FOR CONNECTING THE TOWING CABLE TO THE TARGET; AND MEANS ON SAID BODY MEMBER FOR COOPERATING WITH THE TOWING CABLE TO MAINTAIN THE TARGET AT A DESIRED ROLL ATTITUDE. 